1. Field of the Invention
The present invention generally relates to a high electromagnetic transmission composite structure, and more particularly, to a multi-layer composite structure to decrease the transmission loss efficiency and increase the strength of the structure.
2. Description of the Prior Art
With the development of technology, technologies and applications of the radar also continually are renovated. “RADAR” is transliterating in English, it is the abbreviation of Radio Detection And Ranging, and its original meaning is the wireless exploration and range finding.
However, there are various kinds of radars, and the method of classifying radars is also very complicated. Usually, the radars can be classified into the type for general applications or the type for martial or science research purposes. For example, the general applications comprise management in airport and harbor, weather forecast, and astronomy research; the martial applications comprise hunting and guiding, tracking survey and fire control, identifying whether it is a friend or a foe, downward view, downward shoot and the surveying and drawing navigation of a fighter.
The fundamental theory of the radar is to transmit an electromagnetic wave to a target, and the target will be discovered if a returned wave, a forwarding wave, or a self-radiation of the electromagnetic wave from the target is received, through which the position, velocity, shape, gyrate, or other parameters of the target from the received signal can be retrieved, so that the information on the distance from the target to the radar, the distance variation rate (radial velocity), the position, the altitude will be obtained accordingly. The advantage of the radar is that the radar can measure a distant and small target no matter it is in the daytime or night, and will not be blocked by fog, cloud, or rain.
However, there are various types of energy existing in the space, such as voice, light, and electromagnetic wave. All these types of energy have a common characteristic that if the energy is stronger, the transmitting distance of the energy will be farther. For example, in order to detect the distant target, the general power range of the radar transmitter is 100,000 to 1,000,000 watts, but most energy of the radar signal will be lost in the transmitting process, only a small part of energy of the radar signal can reach the target and the radar signal will be reflected back by the target. And the reflected energy of the reflected signal will be lost again in the transmitting process before it is received by the antenna of the radar, the received signal usually has an energy of 10 to 12 pico-watts only.
Furthermore, the loss of the energy of the electromagnetic wave in the transmitting process can be classified in two types: spreading and absorption. The spreading relates to the transmitting distance, because the electromagnetic wave energy and the disseminating distance square are in reverse proportion. If the transmitting distance is longer, the loss of the electromagnetic wave energy caused by spreading will become more serious. As to the absorption, the absorption relates to natural environment factors such as rainfall, oxygen and steam in the air. Especially, when the rainfall is higher, the electromagnetic wave energy will be absorbed critically. The loss of electromagnetic wave energy is formed according to the oxygen and steam in the air.
Above all, the transmitting energy of the electromagnetic wave will be affected by many factors. Therefore, the radar device is located in an outdoor environment, so that the electromagnetic wave emitted from the radar device will not be blocked by the shelter and causes greater loss. However, in order to reduce the damage of the radar device caused by exposing the radar device in outdoor environment (e.g., rainfall or gale) for a long period of time, a protection structure is usually disposed on the periphery or the outside of the radar device, and it is also called the radome.
However, when the electromagnetic wave emitted by the radar passes through an object, the energy power of the electromagnetic wave will be decreased. Therefore, although the radome can protect the radar device from being damaged by environment influence, the electromagnetic wave emitted by the radar will still be influenced by the radome, so that the detecting efficiency and the judgment accuracy of the radar device will be affected.
Therefore, the high electromagnetic transmission composite structure of the invention uses the multi-layer assembly method to decrease the transmission loss effectively and make the effective operating frequency wider. And, since the high electromagnetic transmission composite structure of the invention has stronger structural strength, it can be widely used in various kinds of radome.